The prior art technique of employing arc discharge devices to produce electrons to initiate a laser discharge at the main electrodes of a laser system requires high power excitation of the arc discharge devices and results in significant heating, while acting non-uniformly on the volume of laser gas flow. While it is desirable to operate planar electrodes of a laser apparatus in a CW or quasi CW mode to achieve desired high power uniform laser discharge, such operation requires a high background electron density. While the arc devices are capable of generating sufficient background electron density to permit quasi CW operation of planar laser electrodes at low pressures, i.e., below 50 Torr, the arc discharge devices are not suitable for uniform discharge operation at pressures above 50 Torr and approaching several atmospheres.
The prior art technology of employing electrons supplied by an electron beam device (gun) to initiate and/or sustain a laser discharge a the main electrodes of a laser system requires the use of high voltages to accelerate electrons to high velocity so that they can penetrate a thin metallic foil and enter a laser optical cavity and, thereby, provide electrons for electron impact excitation. The foil is necessary to provide a seal which separates the very low pressure regions of an electron beam device from the considerably higher pressure regions of a laser excitation cavity. This type of laser has several disadvantages. The required foil is fragile and susceptible to failure by puncture by either arcs or by overheating at high energy loading. Electron beam devices also produce undesirable X-rays. Electron beam lasers also suffer from non-uniformity of optical gain in the laser cavity resulting from non-uniformity of electron density in the cavity. This has an adverse effect on beam divergence and control.